All you can do is ask. If they are not going to cooperate, just let it go.
A similar thing happened to me when I quit my old band. I created (an paid for) everything for that band...demos, videos, logos, website, posters, backdrops, Facebook presence, etc. Two of the guys went on a power trip, and I bailed. After disrespecting me both on stage and online, they just expected me to hand over everything free of charge. Had they simply said "please", I probably would have just handed stuff over. When the drummer found out about their social media exploits, he quit the band and insisted I burn down the website and Facebook page completely. To this day, they use a bastardized version of the logo I created, and they loaded the demos I recorded onto ReverbNation (does anybody even use that website?). I could let it bother me, but instead the drummer and I laugh that that's the best those putzes are ever going to sound.